This paper discusses several evolved micro-loop-gap microwave resonator designs for chip-scale atomic clock applications. Two different schemes have been investigated to develop the LEMAC (LTF-EPFL Miniature Atomic Clock) based on the optical-microwave double resonance, aiming for improving the short-term and long-term stabilities of the counterpart. They show superior performance in terms of size reduction and magnetic field homogeneity for atom transition.